Synthesis and characterization of faujasite zeolite and geopolymer from South African coal fly ash

Abstract

South African coal fly ash (CFA) has been used as a source of silicon and aluminum in the synthesis of faujasite zeolite and geopolymer. However, the synthesis of faujasite zeolite from CFA filtrate does not favor the industrialization of the process because of the small yield of the final product and the huge amount of waste generated. This study suggests a way of synthesizing a pure faujasite and geopolymer from the same batch of CFA. A pure faujasite, with a yield of 43.28%, was synthesized from alumina and silica that were sequentially extracted from CFA using H2SO4 (95–99%) and NaOH (8 M), while the remaining slurry was transformed into a geopolymer. This process shows that a waste material (CFA) can be transformed into two valuable products without major waste generated.